A Terraform Run consists of one or more Resources. Resources are what will actually happen when you enter terraform apply to deploy your configuration.
Terraform Resources are blocks of Infrastructure-as-Code (IaC) elements. These define what the deployment should be and leave it up to the Terraform logic and the provider to make happen. While several aspects of Terraform seem quite similar to a programming language, what you are actually "coding" is how things should be. When you run terraform apply, you are telling Terraform to make them that way.